The present disclosure relates to a method of estimating a state of charge of a secondary cell, a state-of-charge estimation device, a cell pack including the state-of-charge estimation device, an electronic apparatus, and an electric vehicle.
In consideration of user's convenience, a state of charge (SOC) is frequently estimated and displayed in secondary cells. In most of the secondary cells, the state of charge is shown at about three to five stages from a measurement result of a terminal voltage of the secondary cell. Further, secondary cells such as lithium-ion secondary cells are often used in electronic apparatuses such as personal computers, and thus the state of charge is also calculated by current integration.
In general, a state of charge can be estimated by accurately measuring an open voltage (open circuit voltage or open terminal voltage: OCV) of a secondary cell. For example, Japanese Unexamined Patent Application Publication No. 11-204149 discloses a lithium cell remaining capacity measuring method of correcting current dependency of an electromotive force of a lithium cell according to a lithium diffusion concentration gradient in an electrode of the lithium cell based on respective sampling data of the terminal voltage and current of the lithium cell, calculating an open circuit voltage of the lithium cell based on the correction result, and measuring the remaining capacity of a lithium cell based on the open circuit voltage.